diff --git a/src/FluentNHibernate.Specs/Automapping/OverrideSpecs.cs b/src/FluentNHibernate.Specs/Automapping/OverrideSpecs.cs
index 5709782c0..cf93e87c7 100644
--- a/src/FluentNHibernate.Specs/Automapping/OverrideSpecs.cs
+++ b/src/FluentNHibernate.Specs/Automapping/OverrideSpecs.cs
@@ -34,6 +34,30 @@ public class when_using_an_automapping_override_to_create_a_join
         static ClassMapping mapping;
     }
 
+    public class when_using_an_automapping_override_to_specify_a_discriminators_and_join_on_subclass
+    {
+        private Establish context = () =>
+            model = AutoMap.Source(new StubTypeSource(typeof (Parent), typeof (Child)))
+                .Override<Parent>(map =>
+                    map.DiscriminateSubClassesOnColumn("type"))
+                .Override<Child>(map => map.Join("table", part => { }));
+
+        private Because of = () => 
+            mapping = model.BuildMappingFor<Parent>();
+
+        It should_not_create_the_join_mapping = () =>
+            mapping.Joins.Should().BeEmpty();
+
+        It should_map_the_discriminator = () =>
+            mapping.Discriminator.Should().NotBeNull();
+
+        It should_map_subclasses_as_joined_subclasses = () =>
+            mapping.Subclasses.Should().OnlyContain(x => x.Joins.Any());
+
+        static AutoPersistenceModel model;
+        static ClassMapping mapping;
+    }
+
     public class when_using_an_automapping_override_to_specify_a_discriminator
     {
         Establish context = () =>
diff --git a/src/FluentNHibernate/Automapping/AutoMapping.cs b/src/FluentNHibernate/Automapping/AutoMapping.cs
index 43fb707dc..9e20d02e8 100644
--- a/src/FluentNHibernate/Automapping/AutoMapping.cs
+++ b/src/FluentNHibernate/Automapping/AutoMapping.cs
@@ -61,12 +61,12 @@ void IAutoClasslike.AlterModel(ClassMappingBase mapping)
                 if (Cache.IsDirty)
                     classMapping.Set(x => x.Cache, Layer.Defaults, ((ICacheMappingProvider)Cache).GetCacheMapping());
 
-                foreach (var join in providers.Joins)
-                    classMapping.AddJoin(join.GetJoinMapping());
-
                 classMapping.Set(x => x.Tuplizer, Layer.Defaults, providers.TuplizerMapping);
             }
 
+            foreach (var join in providers.Joins)
+                mapping.AddOrReplaceJoin(join.GetJoinMapping());
+
             foreach (var property in providers.Properties)
                 mapping.AddOrReplaceProperty(property.GetPropertyMapping());
 
diff --git a/src/FluentNHibernate/MappingModel/ClassBased/ClassMappingBase.cs b/src/FluentNHibernate/MappingModel/ClassBased/ClassMappingBase.cs
index fa8c8be40..cf1934404 100644
--- a/src/FluentNHibernate/MappingModel/ClassBased/ClassMappingBase.cs
+++ b/src/FluentNHibernate/MappingModel/ClassBased/ClassMappingBase.cs
@@ -146,6 +146,11 @@ public void AddJoin(JoinMapping mapping)
             mappedMembers.AddJoin(mapping);
         }
 
+        public void AddOrReplaceJoin(JoinMapping mapping)
+        {
+            mappedMembers.AddOrReplaceJoin(mapping);
+        }
+
         public void AddFilter(FilterMapping mapping)
         {
             mappedMembers.AddFilter(mapping);
diff --git a/src/FluentNHibernate/MappingModel/MappedMembers.cs b/src/FluentNHibernate/MappingModel/MappedMembers.cs
index 97ead01ca..a386e8154 100644
--- a/src/FluentNHibernate/MappingModel/MappedMembers.cs
+++ b/src/FluentNHibernate/MappingModel/MappedMembers.cs
@@ -132,6 +132,11 @@ public void AddJoin(JoinMapping mapping)
             AddMapping(mapping, MappingType.Join);
         }
 
+        public void AddOrReplaceJoin(JoinMapping mapping)
+        {
+            AddOrReplaceMapping(mapping, MappingType.Join, x => x.TableName == mapping.TableName);
+        }
+
         public void AddFilter(FilterMapping mapping)
         {
             if (Filters.Any(x => x.Name == mapping.Name))